The present invention relates to a tuning fork type crystal component for an angular velocity sensor (hereinafter referred to as an “angular velocity sensor element”) and a manufacturing method thereof, and in particular, to a sensor electrode of the angular velocity sensor element.
Angular velocity sensor elements are generally known which detect electric charge generated in an arm of a tuning fork by so-called Coriolis force when the tuning fork is vibrating. Moreover, angular velocity sensor elements are used for example in vehicle guidance systems, and devices for preventing camera shake, and mass production thereof is advancing.
FIGS. 6A and 6B are drawings describing a conventional example of an angular velocity sensor element, FIG. 6A showing an angular sensor element, and FIG. 6B showing a connection drawing thereof.
As shown in FIG. 6A, this angular velocity sensor element comprises a Z-cut tuning fork shaped crystal element 10 having a pair of tuning fork arms 1a and 1b that extend from a tuning fork base portion 2. Driving electrodes 3a, 3b, and 4a, 4b, which excite tuning fork vibration, are formed on both principal planes and on the inside and outside side faces of one tuning fork arm 1a respectively. The driving electrodes 3a and 3b on the both principal planes and the driving electrodes 4a and 4b on the inside and outside side faces are commonly connected via respective wiring patterns (not shown in the drawing). In this conventional example, the driving electrodes of the inside and outside side faces are made a reference potential.
Moreover, a pair of sensor electrodes that detect electric charge caused by the Coriolis force, are formed on the inside and outside side faces of the other tuning fork arm 1b. As shown in FIG. 6A and FIG. 6B, the pair of sensor electrodes comprises a ground electrode 5 on the inside side face, and electrically separated first and second sensor electrodes 6a and 6b provided on left and right sides of the outside side face. Furthermore, an electric charge generated with inverse sign to the ground electrode 5 in the tuning fork arm 1b, by the bending that occurs in the orthogonal direction to the plate face (principal plane of the tuning fork shaped crystal element 10) due to the Coriolis force, is detected by the first and second sensor electrodes 6a and 6b. 
In particular for the first and second sensor electrodes 6a and 6b which are provided on the outside side face, the area and position need to be formed with a required degree of accuracy. If accuracy of these is not maintained, this can cause a deterioration in uniformity of angular velocity detection sensitivity for the target object, and may also cause generation of unnecessary signals other than the signal originating from the angular velocity.
Also, monitor electrodes 7a and 7b are formed on both principal planes of the other tuning fork arm 1b, for detecting the electric charge due to the amplitude of the tuning fork vibration, to control the amplitude of the tuning fork vibration. In FIG. 6B, reference symbols D1 and D2 denote drive terminals, reference symbols S1 and S2 denote sensor terminals, and reference symbols M1 and M2 denote monitor terminals.
The electrodes are formed for example by setting a mechanically processed individual tuning fork shaped crystal element 10 in a plating frame (not shown in the drawing), and placing this in a vapor deposition apparatus, and then depositing a metallic film on the required places of the crystal element 10. Alternatively, a number of fork shaped crystal elements 10 are integrally formed on a single crystal wafer using a photo-etching technique.
This photo-etching technique generally comprises a photolithography technique (photo-print technique) and a wet etching technique. For example, when forming the tuning fork shaped crystal element 10, a tuning fork shaped hydrofluoric acid resisting mask is formed on the single crystal wafer, and it is immersed in hydrofluoric acid type etchant to remove unwanted parts. Also, when forming the electrodes, a positive or negative photo-resist film (hereinafter referred to as “resist film”) is applied on the metallic film provided on the tuning fork shaped crystal element 10, and selective exposure and development are performed, after which unwanted parts of the metallic film are removed by etching to form each electrode pattern (photolithography technique).
However, in the conventional angular velocity sensor element constructed as described above, forming the electrodes with a plating frame and by deposition depends on mechanical accuracy of the plating frame itself and the framing operation. As a result, naturally there has been a limitation for forming electrodes with a high degree of accuracy, for both principal planes and each side face, particularly including the first and second sensor electrodes 6a and 6b on the outside side face of the other tuning fork arm 1b. When miniaturization of the element is attempted, this problem becomes greater.
Also, when forming the first and second sensor electrodes 6a and 6b on the side face of the tuning fork shaped crystal element 10 using a photo-etching technique, a formation method may be performed in which a single crystal wafer on which the tuning fork shaped crystal element 10 is already formed is exposed from an oblique direction. However, when this method is employed, the exposure equipment becomes larger, and there is an issue in that technical problems and may arise due to the oblique exposure.